Pressure Vessel Boss and Liner Interface

ABSTRACT

A boss for a pressure vessel has a flange. The flange includes an interior keyway having an inner sidewall and a plurality of bores disposed on the inner sidewall. A pressure vessel includes a main body section and an end section. The end section includes a boss and the boss includes a flange. The flange includes an interior keyway having an inner sidewall and a plurality of bores disposed on the inner sidewall. In another aspect, a pressure vessel includes an outer shell, and inner liner and a boss including a flange with an exterior side and an interior side. The liner is mechanically integrated with the flange via a plurality of anchors, each anchor contacting the flange only on the interior side. A method of forming a pressure vessel includes providing a boss having a flange. The flange has an interior keyway having an inner sidewall and a plurality of bores disposed on the inner sidewall. The method comprises allowing a fluid polymer material to flow into the interior keyway and into the plurality of bores.

BACKGROUND

Pressure vessels are commonly used for containing a variety of fluidsunder pressure, such as storing oxygen, natural gas, nitrogen, propaneand other fuels, for example. Suitable container materials includelaminated layers of wound fiberglass filaments or other syntheticfilaments bonded together by a thermal-setting or thermoplastic resin.An elastomeric or other non-metal resilient liner or bladder often isdisposed within the composite shell to seal the vessel and preventinternal fluids from contacting the composite material. The compositeconstruction of the vessels provides numerous advantages such aslightness in weight and resistance to corrosion, fatigue andcatastrophic failure. These attributes are due to the high specificstrengths of the reinforcing fibers or filaments that are typicallyoriented in the direction of the principal forces in the construction ofthe pressure vessels.

FIGS. 1 and 2 illustrate an elongated pressure vessel 10, such as thatdisclosed in U.S. Pat. No. 5,476,189, which is hereby incorporated byreference. Vessel 10 has a main body section 12 with end sections 14. Aboss 16 is provided at one or both ends of the vessel 10 to provide aport for communicating with the interior of the vessel 10. The vessel 10is formed from an inner polymer liner 20 covered by an outer compositeshell 18. In this case, “composite” means a fiber reinforced resinmatrix material, such as a filament wound or laminated structure.

The liner 20 has a generally hemispheroidal end section 22 with anopening 24 aligned within an opening 26 in the outer composite shell 18.Boss 16 is positioned within the aligned openings and includes a neckportion 28 and a radially outwardly projecting flange portion 30. Theboss 16 defines a port 32 through which fluid at high pressure may becommunicated with the interior of the pressure vessel 10.

Liner 20 includes a dual layer lip circumscribing opening 24 in theliner 20, with an outer lip segment 34 and an inner lip segment 36defining an annular recess 38 therebetween for receiving flange portion30 of boss 16. Dovetailed inter-engaging locking means 40 are providedbetween flange portion 30 and outer and inner lip segments 34 and 36,respectively, to lock liner 20 to boss 16.

This type of interlocking liner and boss structure has proved effectivein certain applications, such as for compressed natural gas (CNG) fuelcontainers. However, in high pressure (e.g., 700 bar) service,distortions of the plastic liner material adjacent the boss has beennoted, leading to some tendency of the plastic to be pulled out of thekeyway (i.e., out of the interlocking means 40). The “distortion” ofthis area in high pressure applications comes from the presence of highpressure gas in the keyway between the liner 20 and boss 16. Highpressure gas saturates the liner material and then outgases when thepressure drops. Thus, the gas permeating the area between the liner 20and boss 16 can then have a higher pressure than the gas within vessel10, such as, for example, when gas is being vented from the vessel 10.As a result, the excess pressure between the liner 20 and boss 16 cancause the liner material to be forced out of the keyway. Thus, thereremains a need for a liner and boss interface structure that preventsseparation of the liner and boss under high pressure and that allowsventing of any such gas trapped in the keyway between the liner and theboss.

SUMMARY

In one aspect, the disclosure describes a boss for a pressure vessel,the boss having a flange. The flange comprises an interior keyway havingan inner sidewall and a plurality of bores disposed on the innersidewall.

In another aspect, the disclosure describes a pressure vessel comprisinga main body section and an end section connected to the main body. Theend section comprises a boss and the boss comprises a flange. The flangecomprises an interior keyway having an inner sidewall and a plurality ofbores disposed on the inner sidewall.

In yet another aspect, the disclosure describes a pressure vesselcomprising a composite shell and a boss. The composite shell comprisesan outer shell and an inner liner disposed within the outer shell. Theboss defines a port in the composite shell and comprises a flange withan exterior side and an interior side. The liner is mechanicallyintegrated with the flange via a plurality of anchors, each anchorcontacting the flange only on the interior side thereof.

In yet another aspect, a method of forming a pressure vessel comprisesproviding a boss having a flange. The flange has an interior keywayhaving an inner sidewall and a plurality of bores disposed on the innersidewall. The method comprises allowing a fluid polymer material to flowinto the interior keyway and into the plurality of bores.

This summary is provided to introduce concepts in simplified form thatare further described below in the Detailed Description. This summary isnot intended to identify key features or essential features of thedisclosed or claimed subject matter and is not intended to describe eachdisclosed embodiment or every implementation of the disclosed or claimedsubject matter. Specifically, features disclosed herein with respect toone embodiment may be equally applicable to another. Further, thissummary is not intended to be used as an aid in determining the scope ofthe claimed subject matter. Many other novel advantages, features, andrelationships will become apparent as this description proceeds. Thefigures and the description that follow more particularly exemplifyillustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosed subject matter will be further explained with reference tothe attached figures, wherein like structure or system elements arereferred to by like reference numerals throughout the several views.

FIG. 1 is a side elevation view of a typical elongated pressure vessel.

FIG. 2 is a partial cross-sectional view through one end of such apressure vessel, taken along line 2-2 of FIG. 1.

FIG. 3 is a perspective view of a first embodiment of a boss of thepresent disclosure.

FIG. 4A is a partial cross-sectional view through the boss of FIG. 3,taken along line 44.

FIG. 4B is similar to FIG. 4A but shows the boss connected to a vesselliner.

FIG. 5 is a perspective view of a second embodiment of a boss of thepresent disclosure.

FIG. 6A is a partial cross-sectional view through the boss of FIG. 5,taken along line 6-6.

FIG. 6B is similar to FIG. 6A but shows the boss connected to a vesselliner.

While the above-identified figures set forth one or more embodiments ofthe disclosed subject matter, other embodiments are also contemplated,as noted in the disclosure. In all cases, this disclosure presents thedisclosed subject matter by way of representation and not limitation. Itshould be understood that numerous other modifications and embodimentscan be devised by those skilled in the art which fall within the scopeand spirit of the principles of this disclosure.

The figures may not be drawn to scale. Moreover, where terms such asabove, below, over, under, top, bottom, side, right, left, etc., areused, it is to be understood that they are used only for ease ofunderstanding the description. It is contemplated that structures may beotherwise oriented.

DETAILED DESCRIPTION

In one embodiment, an improved boss and liner interface structure isillustrated on boss 16A of FIGS. 3, 4A and 4B. Annular external orexterior keyway 42 and annular internal or interior keyway 44 areprovided on flange 30 to mate with interlocking keys 42 a and 44 a ofliner 20, respectively. As used in this disclosure, the term “dovetail”describes a keyway or interlocking key configuration comprising a lip,notch, flare, projection or similar or corresponding structure so that ajoint formed between the keyway 42/44 of boss 16A and interlocking keys42 a/44 a of liner 20 is structurally inhibited from separation.External keyway 42 includes annular lip 52 extending in an axialdirection to prevent separation in the radial direction and annular lip54 extending in a radial direction to prevent separation in the axialdirection. Similarly, internal keyway 44 includes annular lip 56extending in an axial direction to prevent separation in the radialdirection and annular lip 58 extending in a radial direction to preventseparation in the axial direction.

An annular groove 46 is defined on an interior side of flange 30A ofboss 16A, radially inwardly of internal keyway 44. Groove 46 isconnected to internal keyway 44 by means of a plurality of discretebores 48 formed between inner sidewall 50 of internal keyway 44 andgroove 46, with each bore 48 having, at one end thereof, a first opening48 a in internal keyway 44 and, at a second end thereof, a secondopening in groove 46. In cross-section, bores 48 may be circular orelongated, for example. In an exemplary embodiment, groove 46 issubstantially “V”-shaped.

A method of forming a pressure vessel 10 includes allowing a fluidpolymer material for liner 20 to flow into and fill the external keyway,42, internal keyway 44, groove 46 and bores 48. The liner material thensolidifies, thereby forming key 42 a, key 44 a and anchor 49. Liner 20is mechanically interlocked with boss 16A by anchors 49 formed withinbores 48, connecting the liner material in groove 46 with the linermaterial in internal keyway 44 (key 44 a). Accordingly, even underextreme pressure conditions, separation of liner 20 from boss 16A isprevented. In effect, the liner material 20 would need to tear apartbefore separation of liner 20 and boss 16A could occur.

Flange 30A has an interior side 60 and an exterior side 62. In anexemplary embodiment, each anchor 49 contacts only the interior side ofthe flange 30A, and does not contact the exterior side of the flange30A. Because internal keyway 44, groove 46 and bores 48 are all locatedon the interior side 60 of flange 30A, there is no passage for gasleakage from the interior side of flange 30A to the exterior side offlange 30A. Moreover, any built-up gas between liner 20 and boss 16A canescape back into vessel 10 at opening 24 of liner 20 (see FIG. 2),thereby preventing a rupture or separation at the interface of liner 20and boss 16A.

Another exemplary boss of the present disclosure is illustrated in FIGS.5, 6A and 6B. This exemplary boss 16B construction is similar to that ofboss 16A, discussed above, except that no groove is provided radiallyinwardly of the inner keyway 44. Within that inner keyway 44, aplurality of discrete bores 48 are provided in the boss 16B in a nearradial direction, via openings 48 a in sidewall 50 of the keyway 44. Asused herein, a “bore” need not extend all the way through a member. Assuch, the bore 48 may extend from its openings 48 a to a closed endthereof, as at 48 c in FIGS. 6A and 6B. As vessel 10 is formed, thematerial of liner 20 again forms annular keys that flow into andinterlock with annular keyways 42 and 44 (external key 42 b and internalkey 44 b, respectively). From internal key 44 b, liner material fillsbores 48 to form anchors 49 for preventing the separation of boss 16Band liner 20.

Each of the boss constructions discussed above (the boss 16A illustratedin FIGS. 3, 4A and 4B and the boss 16B illustrated in FIGS. 5, 6A and6B) is intended to provide a highly stable and integrated interfacebetween the boss 16A/B and liner 20, in order to prevent blowout and/orgas buildup between the boss 16A/B and liner 20.

Although the subject of this disclosure has been described withreference to several embodiments, workers skilled in the art willrecognize that changes may be made in form and detail without departingfrom the spirit and scope of the disclosure. In addition, any featuredisclosed with respect to one embodiment may be incorporated in anotherembodiment, and vice-versa. For example, some bores may extend all theway through a portion of the flange (such as shown, for example, inFIGS. 3, 4A and 4B) while others do not (such as shown, for example, inFIGS. 5, 6A and 6B). Bore configurations may alternate radially aroundthe flange (all-the-way-through bore, closed-end bore,all-the-way-through bore, etc.) or may be arranged in any otherintermingled bore configuration arrangement about the flange.

1. A boss for a pressure vessel, the boss having a flange comprising: aninterior keyway having an inner sidewall; and a plurality of boresdisposed on the inner sidewall.
 2. The boss of claim 1 furthercomprising a groove disposed radially inward of the interior keyway, theplurality of bores connecting the interior keyway and the groove.
 3. Theboss of claim 2 wherein the groove is “V”-shaped.
 4. The boss of claim 1wherein the interior keyway comprises a lip extending in an axialdirection.
 5. The boss of claim 1 wherein the interior keyway comprisesa lip extending in a radial direction.
 6. The boss of claim 1 furthercomprising an exterior keyway.
 7. The boss of claim 6 wherein theexterior keyway comprises a lip extending in an axial direction.
 8. Theboss of claim 6 wherein the exterior keyway comprises a lip extending ina radial direction.
 9. The boss of claim 1 wherein each bore has a firstopening for that bore extending into the flange of the boss.
 10. Theboss of claim 1 wherein at least one bore extends through a portion ofthe flange to a second opening for that bore on an interior side of theflange.
 11. The boss of claim 10 wherein each second opening is disposedin an annular groove on the interior side of the flange.
 12. The boss ofclaim 10 wherein each bore extends through the portion of the flange tothe second opening for that bore on an interior side of the flange. 13.The boss of claim 9 wherein at least one bore extends into a portion ofthe flange to a second closed end of the bore within the flange.
 14. Apressure vessel comprising: a main body section; and an end sectionconnected to the main body section, the end section comprising a boss,the boss comprising a flange, the flange comprising: an interior keywayhaving an inner sidewall; and a plurality of bores disposed on the innersidewall.
 15. The vessel of claim 14 further comprising a groovedisposed radially inward of the interior keyway, the plurality of boresconnecting the interior keyway and the groove.
 16. The vessel of claim15 wherein the groove is “V”-shaped.
 17. The vessel of claim 14 whereinthe interior keyway comprises a lip extending in an axial direction. 18.The vessel of claim 14 wherein the interior keyway comprises a lipextending in a radial direction.
 19. The vessel of claim 14 furthercomprising an exterior keyway.
 20. The vessel of claim 19 wherein theexterior keyway comprises a lip extending in an axial direction.
 21. Thevessel of claim 14 wherein the exterior keyway comprises a lip extendingin a radial direction.
 22. A pressure vessel comprising: a compositeshell comprising: an outer shell; and an inner liner disposed within theouter shell; and a boss defining a port in the composite shell, the bosscomprising a flange with an exterior side and an interior side, whereinthe liner is mechanically integrated with the flange via a plurality ofanchors, each anchor contacting the flange only on the interior sidethereof.
 23. A method of forming a pressure vessel comprising: providinga boss having a flange comprising: an interior keyway having an innersidewall; and a plurality of bores disposed on the inner sidewall;allowing a fluid polymer material to flow into the interior keyway andinto the plurality of bores.
 24. The method of claim 23 wherein the bossfurther comprises a groove disposed radially inward of the interiorkeyway, at least some of the plurality of bores connecting the interiorkeyway and the groove, the method comprising allowing the fluid polymermaterial to fill the interior keyway, the groove, and the at least someof the plurality of bores.